In QuickBooks Online, I can navigate to Expenses > Vendors and edit a Vendor to include a Default Expense Category (at the bottom of the form, under the "Accounting" heading).

I would expect QB to automatically enter this Expense Category when I manually enter a new "expense" enter at the bottom of the checking account register. Not so much. What am I missing?

The bigger issue I'm trying to solve is this: I am just using QuickBooks to record and categorize income and expenses that flow through our checking and savings accounts. The easiest view for me to use is the "register" view. I want to use the "add ..." feature at the bottom of the register to enter transactions. Can I teach QB to fill in details of a transaction after I enter the payee/vendor/employee name?